This invention relates to a fuel injection device for use in compression ignition engines such as the Diesel engine.
In recent years, the nitrogen oxides entrained by the exhaust gas from engines are causing such serious environmental pollution as to cause the adoption of legal countermeasures. For Diesel engines, there have been proposed many methods for controlling the formation of nitrogen oxides in the exhaust gas. One method comprises having one combustion chamber provided with a plurality of injection nozzles and allowing the fuel to be simultaneously injected from the plurality of injection nozzles into the combustion chamber. Another method comprises having one combustion chamber provided with a plurality of injection nozzles and one plunger pump and allowing the fuel to be injected into the combustion chamber in a multistage manner (Japanese Patent Laid-open Publication No. 119103/1975 and No. 119130/1975). Still another method comprises connecting one injection nozzle with or two injection nozzles respectively with two injection systems having different injection ratios and allowing the fuel to be fed from the injection systems to the injection nozzle(s) (Japanese Patent Laid-open Publication No. 28331/1972 and No. 83219/1973). Still another method comprises having one combustion chamber provided with a plurality of injection nozzles and as many plunger pumps and allowing the fuel to be injected into the combustion chamber at fixed time intervals on a staggered time schedule (Japanese Patent Publication No. 5513/1957 and No. 43650/1974).
In the engines designed for working the methods described above, the time intervals are invariably fixed without reference to the conditions under which the engine is put to operation. Accordingly, when the conditions have been varied, it has been difficult to obtain effective control of the formation of nitrogen oxides in the exhaust gas with these methods.
An object of this invention is to provide a fuel injection device for a compression ignition engine having one combustion chamber with a plurality of injection nozzles and as many plunger pumps, which device is adapted to cause the time intervals at which the plurality of injection nozzles inject fuel into the combustion chamber to automatically be optimized in accordance with the variable conditions under which the engine is put to operation to thereby ensure efficient combustion of fuel and effective control of the formation of nitrogen oxides in the exhaust gas.
In case where the timing of the injection of fuel into the combustion chamber is varied with the increase in the rotational speed of the engine, for example, the device according to the present invention can adjust the time intervals to be optimized so that effective control of the formation of nitrogen oxides and effective combustion can be obtained.
The term "time interval" used throughout the specification means the interval between the time the fuel is injected from one of the injection nozzles and the time it is injected from another injection nozzle.